The invention relates to a collapsible core to be attached to a mold half of a casting mold, in particular a die casting mold, and to a casting mold half equipped with such a collapsible core.
Collapsible cores of this type, which are also referred to as foldable cores, have heretofore typically been used in plastic injection molding technology to be able to produce plastic parts which have undercuts, for example, a thread. A known type of collapsible core has a core cylinder body for this purpose, which essentially extends axially out from a base body and contains an axially movable middle core and a plurality of axially immovable core segments surrounding it. In the case of such a collapsible core, as is disclosed in published application DE 10 2011 011 784 A1, the middle core has the form of a truncated cone, wherein the core segments are guided in a formfitting manner by means of dovetail guides on the cone jacket of the middle core so that they execute the desired collapsing movement toward the longitudinal center axis of the collapsible core in the event of axial movement of the middle core. As core segments, three wider main segments alternate with three narrower intermediate segments alternately in the circumferential direction of the middle core, wherein the main segments are guided on first wedge faces of the middle core and the intermediate segments are guided on second wedge faces of the middle core having greater wedge angle in relation to the first wedge faces. Each intermediate segment has a cross section, which tapers conically outward radially and accordingly has lateral edges inclined in a V shape in relation to one another, which function as stop faces, with which it presses against corresponding stop faces of the two adjoining main segments. The main segments have acute edge angles between outer face and stop face of approximately 50°. When the middle core is moved back axially, the intermediate segments slide radially inward with their stop faces along the main segments' stop faces in relation to the main segments, and the main segments can in turn be displaced somewhat radially inward.
This known type of collapsible core is designed for use in plastic injection molding and is not intended and is generally also not suitable for use in metal die casting technology. A use in metal die casting technology thus requires that the collapsible core must withstand the significantly higher pressures than plastic injection molding, which typically prevail therein, for which typical plastic injection molding collapsible cores are not designed.
Patent specification DE 197 45 516 C2 discloses a collapsible core usable in an injection mold or casting mold, in which at least two slider elements are held so they are radially immovable in a core cylinder body to implement at least one undercut on the injection molded part or cast part to be produced. The core cylinder body is divided into a main body, on which a first slider element is arranged, and a core head, which is axially moved in front of the main body during the demolding, and on which a second slider element is arranged. The demolding movement of the first slider element radially outward is caused by a control rod guided through the main body, and that for the second slider element is caused by a similar further control rod or by the axial demolding movement of the core head with the use of suitable guide means. An associated head tappet is guided through the longitudinal center through the main body for the axial actuation of the core head.
The above-mentioned conventional collapsible cores are installed permanently in an associated casting mold half and therefore cannot be removed from the casting mold half in running casting operation. Rather, the entire casting mold half must be removed from the casting machine and disassembled for this purpose.
In metal die casting technology, there are applications in which the casting mold surface defining the mold cavity is at least regionally provided with a coating material, which is then transferred by the coating operation to a surface region of the component to be cast.
The invention is based on the technical problem of providing a collapsible core of the type mentioned at the outset having expanded possible applications, in particular also in metal die casting technology, and also a casting mold half equipped therewith.
The invention solves this problem by providing a collapsible core in accordance with embodiments of the invention, and also a casting mold half in accordance with embodiments of the invention.
According to a corresponding aspect of the invention, the collapsible core is embodied as a collapsible core which is removable from the associated casting mold half, wherein it can be detachably attached to the relevant mold half on the mold cavity side, i.e., from the side of the casting mold half facing toward the mold cavity or the opposing casting mold half. This makes it possible to remove the collapsible core in running operation between two casting cycles from the associated casting mold half and to attach it or another collapsible core according to the invention detachably again thereafter. In other words, this collapsible core can be replaced or removed and attached again as an interchangeable kit on the associated casting mold half during casting operation between each two casting cycles, without the casting mold half having to be removed and disassembled as a whole for this purpose.
This advantageous property of the collapsible core implemented in this manner may be utilized, for example, in metal die casting technology to remove the collapsible core from the casting mold half between two casting cycles, to provide it with a coating material to be transferred to the component to be cast, and to then install it from the front again on the casting mold half, so that in the subsequent casting cycle, the coating material can be transferred from the collapsible core to the component to be cast. The removable attachment of the collapsible core to the casting mold half enables the collapsible core to be brought to the location in this case at which the coating material is kept ready, so that the collapsible core does not have to be provided with the coating material in its location installed on the casting mold half.
In one embodiment of this measure according to the invention, the collapsible core has a latching element for a latch connection to the mold half. This advantageously provides the condition that the collapsible core can be detachably attached in a latching manner on the associated casting mold half.
In a further aspect, the invention provides a collapsible core, which has a core cylinder body made of at least two first core jaws in the form of cylinder segments and at least two second core jaws in the form of cylinder segments, which are arranged alternately thereto in the circumferential direction, wherein the first and the second core jaws are held in a relatively movable manner against one another. In this case, the relative movement between the first and the second core jaws includes an axial relative movement component between the first and the second core jaws and a radial collapsing movement of the first and/or the second core jaws.
Since, in this collapsible core according to the invention, the core jaws are held in a relatively movable manner against one another, a movable middle core is not required. In contrast to the conventional collapsible cores provided with a middle core, in this collapsible core, the radial collapsing movement is induced by the axial relative movement component of the core jaws in the form of cylinder segments themselves and not by an axial movement of a middle core. For this purpose, the first and the second core jaws are guided against one another suitably. The collapsible core characterized in this manner may advantageously be structurally embodied so that it can also withstand the comparatively high pressures of metal die casting operations without problems. It is apparent that this collapsible core can preferably be embodied as a removable collapsible core corresponding to the above-mentioned first aspect of the invention.
In a refinement, the collapsible core has a base body, from which the core cylinder body extends essentially axially. In this case, facing away from the base body in the axial direction, the first core jaws have a conically decreasing segment width and the second core jaws have a corresponding conically increasing segment width or, vice versa, the first core jaws have a conically increasing segment width and the second core jaws have a corresponding conically decreasing segment width. This represents a structurally simple solution, for inducing the desired radial collapsing movement for the collapsible core by way of the axial relative movement component of the first core jaws in relation to the second core jaws.
In a refinement of the invention, the second core jaws have receptacle means for a core jaw push rod of the associated mold half. This provides the condition for causing the relative movement between the first and the second core jaws, which is required for the radial collapsing movement of the core jaws, by means of the core jaw push rod.
In a refinement of the invention, the first and second core jaws are guided against one another by formfitting guide devices acting between them. For this purpose, these guide devices can each include, for example, a guide groove having T-shaped or L-shaped cross-section or dovetail cross section on a first or second core jaw and a guide web, which is accommodated in the guide groove, having corresponding cross section on an adjoining second or first core jaw, respectively. Each first core jaw is thus securely guided laterally on the two adjoining second core jaws, and in the same manner, each second core jaw is securely guided laterally on the two adjoining first core jaws.
In a refinement of the invention, the first and second core jaws have, on the lateral edges thereof, angles in relation to the outer and inner edges which are all greater than 60°. This construction measure has a very advantageous effect with respect to a high compressive strength of the collapsible core.
A casting mold half according to the invention has a collapsible core receptacle, in which the collapsible core according to the invention is detachably insertable from the mold cavity side. As stated, this enables a removal and reattachment of the collapsible core from or on, respectively, the casting mold half between casting cycles in running casting operation, without the casting mold half having to be removed and disassembled for this purpose.
In a refinement of the invention, the casting mold half has the above-mentioned core jaw push rod and an ejector device, to which the core jaw push rod is coupled. The core jaw relative movement for inducing the radial collapsing movement of the collapsible core can thus be caused while utilizing the ejector device.
In a refinement of the invention, the casting mold half has a latching element, which interacts with the mentioned collapsible core latching element, an ejector device, and a release element, which is coupled to the ejector device. Using the release element, the latch connection formed by the interacting latching elements can be disengaged automatically, i.e., under the effect of the ejector device. This advantageously enables a prior movement of the collapsible core in the scope of a corresponding demolding operation and, if needed, the removal of the released collapsible core from the casting mold half.